1. Field of the Invention
The present invention relates to a cardboard tampon applicator. More particularly, the present invention relates to a cardboard or paper laminate tampon applicator that is coated with a nitrocellulose coating. The applicator preferably has a pierce-through or perforation type fingergrip. The nitrocellulose coated cardboard tampon applicator of the present invention can be formed inexpensively, and will have a high degree of gloss and slip for easier insertion, as well as improved cross-sectional circularity for reduced ejection force.
2. Description of the Prior Art
Tampon applicators are generally formed either from a molded thermoplastic material, such as plastic, or a paper laminate, such as cardboard or paperboard.
It is desired that tampon applicators have a generally circular cross-sectional shape. Maintaining this generally circular shape has been found to reduce the force needed to eject the tampon pledget from the applicator, thus making the tampon applicator more acceptable to the consumer. Well known methods exist to produce molded plastic applicators with regular and consistent cross-section. Moreover, such molded plastic applicators can be formed with a high degree of surface smoothness, which results in increased comfort during insertion of the tampon. However, plastic tampon applicators are neither water dispersible nor biodegradable in any practical sense, unless certain expensive plastics are used. Yet in an ecology-minded society, biodegradability is desirable.
To obtain a biodegradable tampon applicator, paper laminates, such as cardboard, are preferred since such applicators delaminate upon saturation with water. This delamination facilitates the process of biodegradation. To approximate the aesthetics and ease of insertion of plastic tampon applicators, paper applicators are conventionally formed with an outer film layer that is bonded to the applicator by adhesive or the like. However, it is difficult to manufacture a film laminated paper applicator with a perfectly circular cross-section, and the degree of circularity of the laminated paper applicator has been found to degrade further during the tube-forming heating stage of the manufacturing process. Moreover, the applicator is enhanced by including a fingergrip on the barrel of the applicator. However, it has been found to be difficult to produce a fingergrip that is sufficiently grippable.
Alternatively, some commercially available cardboard applicators have a coating that is applied as a liquid and subsequently solidifies on the applicator. For example, liquid wax coatings are inexpensive to apply, and will not degrade the circularity of the tampon applicator during the manufacturing process. However, such liquid wax-coated tampon applicators do not have sufficient surface smoothness and, therefore, do not provide the desired insertion comfort and reduced ejection force.
A polyester film coating that has been used on commercially available tampon applicators has been found to shrink during the heating cycle of the applicator manufacturing process, causing distortion of the applicator's shape. As discussed above, this distortion of the applicator's circular cross-section increases the ejection force required. Cellophane film, also known in the art for use on paper tampon applicators, similarly shrinks due to the evaporation of water absorbed from the adhesive used to apply it to the applicator. Furthermore, the hydrophilic cellophane coating on applicators provide poor insertion comfort. Consequently, cellophane is usually coated with a water resistant coating to improve insertion comfort, discussed further below. Coated cellophane is relatively expensive because it requires a supplemental coating on top of a base layer. In addition, the use of such a coating can require special handling and disposal procedures, all of which further raise manufacturing costs.
Coated paper laminate applicators are known in the art. For example, U.S. Pat. No. 4,412,833 to Weigner et al. is directed to an applicator formed of a high-gloss paper that can be coated with a degradable, dispersible or water soluble polymer, such as a modified polyethylene, polypropylene, polyvinylidene chloride or polyvinyl alcohol.
U.S. Pat. No. 4,508,531 to Whitehead provides an applicator with a heat-sensitive coating, such as a polyolefin (e.g., polyethylene or polypropylene) or a heat sensitive adhesive.
U.S. Pat. No. 4,622,030 to Shelton provides a thermoplastic coated paper tube. A film layer on a paper laminate tampon applicator is disclosed in U.S. Pat. No. 5,346,468 to Campion et al. This paper laminate tampon applicator has a thermoset polymer film layer adhered to the outer surface of the cardboard applicator. Preferably, this polymer film layer is a cellophane layer. A film layer of a thermoplastic polymer such as polyethylene, polyester, polypropylene, polycaprolactone or ethylene vinyl acetate can allegedly be used in place of cellophane.
As an ancillary component, this patent discloses a water resistant coating for use on top of the cellophane layer. This water resistant coating may include polyvinylidine chloride or nitrocellulose. The patent further discloses that a nitrocellulose-coated cellophane sheet is commercially available from Flexel. However, the patent does not suggest the use of a nitrocellulose coating directly on a cardboard tampon applicator. Moreover, it does not suggest a nitrocellulose-based coating containing other components.
Thus, a nitrocellulose coating is known for use in providing water-resistance to a cellophane film layer applied to a tampon applicator. However, no applicator is known that has a nitrocellulose coating applied to the outer paper lamina. Moreover, even the known cellophane film-coated applicator does not have the multiple puncture fingergrip of the present applicator and may not appreciate the significant circularity improvement provided by a nitrocellulose coating applied directly to the outer paper lamina of the applicator.
Thus, the liquid and film coatings described above have not enabled the combination of formation of the desired glossy finish, retention of applicator circularity, desired insertion comfort and desired fingergrip, and sufficient biodegradability. Further, many prior art liquid coatings and compound coatings are more expensive to use.
The present invention is directed to applying a liquid nitrocellulose coat on the surface of the paper laminate applicator, and thereafter optionally forming a multiple puncture fingergrip on the applicator. The applicator thus formed has the desired high gloss finish and maintains the improved degree of circularity of the applicator, while still permitting water dispersibility and biodegradability. The liquid coating of the present invention provides for the formation of the multiple puncture fingergrip, is inexpensive to apply, and does not require the use of organic solvents in the manufacturing process.